This application relates to the field of toxic waste control and more particularly to systems and methods for containing or diverting toxic waste materials stored within the Earth.
Methods and systems for containing toxic waste materials in the Earth are known. For example, U.S. Pat. Nos. 4,860,544 and 4,974,425 to Krieget al. disclose methods and systems for reversibly establishing a flow-impervious cryogenic barrier about a volume within the Earth below a surface region or containment site. The systems include an array of boreholes peripherally established around the containment site and extending down into the Earth about a volume underlying that site. Preferably the boreholes have casings extending therethrough. A refrigerant flow through the boreholes is then established, so that moisture naturally present within the Earth adjacent to the boreholes freezes to form ice columns extending along and about the respective boreholes. The boreholes am spaced and the refrigerant flow controlled so that the adjacent ice columns overlap to form a continuous ice wall, thereby creating a flow-impervious barrier to the migration of contained materials.
Particular problems are encountered in the storage and containment of toxic materials in porous or arid soils within the Earth, such as in volcanic rock or sand. There is relatively little moisture present in such soils, and thus it can be difficult or impossible to establish ice columns or other subterranean frozen regions to assist in the containment or storage of migratory materials.
Krieg et al. discloses, in U.S. Pat. No. 4,974,425, the addition of moisture to porous soil in order to provide sufficient residual water to establish ice columns within the Earth around the refrigerant-containing boreholes. However, the behavior of liquids which are added to porous soils can be difficult to predict and control because there is no convenient or natural way to contain and/or channel such added liquids. As a result, the addition of water to porous soils can, under some circumstances, induce uncontrolled migration of toxic and other materials already present within the soil, potentially causing harm to subterranean aquifers and other structures. Further, environmental legislation has created significant disincentives to introduce a quantity of water into the Earth without providing for its removal and the restoration of the site to its original condition. The addition of water can be sequenced using the techniques of U.S. Pat. No. 4,974,425, particularly with a double barrier, to reduce the danger of added water escaping from the site. However, improvements to such techniques would be very useful.
Accordingly, it is an object of this invention to provide an improved cryogenic barrier system and method for the control and storage of migratory materials within the Earth.
It is another object of the invention to provide an improved cryogenic barrier system and method which effectively prevents the migration of liquids through it.
It is another object of the invention to provide an improved cryogenic barrier system and method which can be reversibly established in the Earth, i.e., which can be readily created and removed.
It is another object of the invention to provide an improved cryogenic barrier system and method which can be created in arid or porous soils.
It is another object of the invention to provide an improved cryogenic barrier system and method which is effective over a long term.
It is another object of the invention to provide an improved cryogenic barrier system and method that is economic and efficient to install and operate.
It is another object of the invention to provide an improved cryogenic barrier system and method that permits integrity monitoring and correction of potential faults or short-term failures before they actually occur.
It is another object of the invention to provide a nonporous, substantially liquid impermeable diverting wall within the Earth for diverting or channeling the migration of materials within the Earth.
These and other advantages will be further detailed in the description and drawings which follow.